NCERT · Science · Ch.3

Atoms and Molecules
MCQ MASTER SERIES

Dalton's Theory · Atomic Mass · Molecules · Mole Concept · Chemical Formulae

⚡ Start Quiz 📊 Analytics
50
Total Questions
30 min
Suggested Time
3
Difficulty Tiers
5
Core Topics
Question Intelligence

Quiz Analytics

A data-driven breakdown of all 50 questions by difficulty, exam origin and topic distribution.

📈 Distribution Overview

50
Total Questions
CBSE Board
25
State Board
16
Olympiad Level
9

🗂 Topic Coverage

Laws of Chemical Combination
18%
Dalton's Atomic Theory
16%
Atomic & Molecular Mass
18%
Chemical Formulae
18%
Mole Concept
30%
25
CBSE Board
16
State Board
9
Olympiad Level
Conceptual Framework

Key Concept Highlights

6 foundational pillars that power every question in this quiz. Understand these, and the answers follow naturally.

⚖️
Laws of Chemical Combination
Law of Conservation of Mass: matter is neither created nor destroyed. Law of Constant Proportions: a compound always contains elements in fixed mass ratios.
⚛️
Dalton's Atomic Theory
Matter is made of atoms (indivisible). Atoms of an element are identical. Atoms combine in whole-number ratios to form compounds. Atom is conserved in chemical reactions.
⚖️
Atomic Mass
Expressed in atomic mass units (u). 1 u = 1/12 mass of C-12 atom. Relative atomic masses: H=1, C=12, O=16, N=14, Na=23, Ca=40, Fe=56.
🔗
Molecules & Formulae
Molecule = smallest unit of an element/compound that can exist independently. Molecular formula shows type and number of atoms. Valency determines bonding capacity.
🧮
Mole Concept
1 mole = 6.022 × 10²³ particles (Avogadro's number). Molar mass = atomic/molecular mass in grams. 1 mole of any gas at STP = 22.4 L.
📐
Molar Mass Calculations
Molar mass = sum of atomic masses of all atoms in the formula. Eg: H₂O = 2(1) + 16 = 18 g/mol. Used to convert between moles, mass, and number of particles.
Pedagogical Value

Why MCQs Matter

Multiple-choice questions are not mere guessing games — they are the sharpest diagnostic tool available to a competitive exam aspirant.

🎯

Precision Recall

Vague understanding doesn't survive MCQs — they force exact conceptual clarity.

⚡

Exam Format Mirror

Direct simulation of CBSE Board objective sections and JEE Main Paper 1 structure.

📊

Exam Weight

~12%

of CBSE Class IX Science — mole concept numericals are highest-yield

Quick Reference

Important Formula Capsules

4 must-memorise equations that surface repeatedly across CBSE and JEE papers.

Moles from Mass
\[ n = \dfrac{\text{given mass (g)}}{\text{molar mass (g/mol)}} \]
Number of Particles
\[ N = n \times N_A = n \times 6.022 \times 10^{23} \]
Volume at STP
\[ V = n \times 22.4\ \text{L} \quad (\text{gases at STP}) \]
Avogadro Number
\[ N_A = 6.022 \times 10^{23}\ \text{mol}^{-1} \]
Learning Outcomes

What You Will Learn

By completing this quiz set you will have exercised all the following competencies.

01 State the Law of Conservation of Mass and the Law of Constant Proportions with examples
02 List the main postulates of Dalton's atomic theory and identify its limitations
03 Define atomic mass unit and calculate the atomic mass of common elements
04 Write chemical formulae using valencies of given elements
05 Define mole and convert between moles, mass, number of particles, and volume
06 Calculate the molecular mass of compounds and use it in stoichiometric calculations
Exam Preparation

Strategy & Preparation Tips

4 evidence-based strategies to maximise your score in CBSE Boards and JEE.

Step 01
Atomic Masses by Heart
Memorise: H=1, He=4, C=12, N=14, O=16, Na=23, Mg=24, Al=27, S=32, Cl=35.5, K=39, Ca=40, Fe=56, Cu=64, Zn=65. These 15 values cover 90% of numericals.
Step 02
Mole Triangle
Draw a triangle: MASS at top, MOLES bottom-left, PARTICLES bottom-right. Mass ÷ molar mass = moles; moles × Nₐ = particles. This triangle solves every mole MCQ.
Step 03
Formula Writing Practice
Practise writing formulae for 20 compounds using criss-cross valency method. Common mistakes: CaCl₂ (not CaCl), Al₂O₃ (not AlO), Fe₂(SO₄)₃.
Step 04
Distinguish the Two Laws
Conservation of Mass = TOTAL mass before = after. Constant Proportions = RATIO of elements is always fixed in a compound. MCQs test which law applies to a given scenario.

Ready to Test Your Mastery?

50 questions  ·  Elapsed timer  ·  Instant scored results

⚡ Begin Atoms and Molecules Quiz
🎯 Knowledge Check

Science — Atoms And Molecules

50 Questions Class 9 MCQs
1
Who gave the law of conservation of mass?
2
The law of definite proportions was given by:
3
Who proposed the atomic theory?
4
According to Dalton’s atomic theory, atoms of different elements:
5
Which of the following is a triatomic molecule?
6
The smallest particle of an element that can take part in a chemical reaction is called:
7
The symbol of sodium is derived from its Latin name:
8
The formula of water is:
9
The molecular mass of \(\mathrm{CO_2}\) is:
10
Which of the following is a polyatomic ion?
11
The atomic mass unit (amu) is based on:
12
The chemical formula of calcium hydroxide is:
13
Who gave the law of multiple proportions?
14
The number of atoms in one molecule of ammonia \(\mathrm{(NH_3)}\) is:
15
The valency of oxygen is:
16
The chemical formula of sulphuric acid is:
17
Avogadro’s number represents:
18
The molecular formula of glucose is:
19
The ratio of hydrogen to oxygen in water by mass is:
20
The total number of atoms in one molecule of \(\mathrm{CO_2}\) is:
21
The formula of magnesium chloride is:
22
Which of the following is a diatomic molecule?
23
One mole of any substance contains:
24
The molecular mass of \(\mathrm{H_2SO_4}\) is:
25
Which law states that mass can neither be created nor destroyed?
26
The combining capacity of an element is called its:
27
The formula of aluminium oxide is:
28
The relative atomic mass of an element is the ratio of the average mass of one atom to:
29
The molecular formula of methane is:
30
The symbol 'S' represents:
31
Which of the following is a compound?
32
The chemical formula of carbon dioxide is:
33
Which of the following correctly represents a molecule of an element?
34
The atomicity of phosphorus \(\mathrm{(P_4)}\) is:
35
The mass of one mole of water is:
36
The molecular formula of hydrogen peroxide is:
37
The term ‘molecule’ is best defined as:
38
The total number of atoms in one molecule of glucose \(\mathrm{(C_6H_12O_6)}\) is:
39
The atomic mass of oxygen is:
40
The number of moles in 18 g of water is:
41
Which of the following statements is correct according to Dalton’s theory?
42
The formula of ammonium sulphate is:
43
The molecular formula of sulphur dioxide is:
44
The number of atoms in one mole of oxygen gas \(\mathrm{(O_2)}\) is:
45
Which of the following is not a correct chemical formula?
46
Which of the following is a cation?
47
The number of hydrogen atoms in 1 molecule of \(\mathrm{C_2H_6}\) is:
48
The valency of aluminium is:
49
The molecular mass of calcium carbonate \(\mathrm{(CaCO_3)}\) is:
50
Which of the following pairs of elements form a compound in a 1:1 ratio?
📚
ACADEMIA AETERNUM तमसो मा ज्योतिर्गमय · Est. 2025
Sharing this chapter
Atoms And Molecules | Science Class 9 | Academia Aeternum
Atoms And Molecules | Science Class 9 | Academia Aeternum — Complete Notes & Solutions · academia-aeternum.com
Understanding the concepts of atoms and molecules is a fundamental part of Class 9 Science. Chapter 3 of NCERT introduces learners to the building blocks of matter — how elements combine, the laws of chemical combination, and how to calculate molecular masses. To help students master these topics, this comprehensive set of 50 multiple choice questions (MCQs) with answers and detailed explanations covers every key concept from the chapter. These questions are ideal for CBSE Class 9 exams, school…
🎓 Class 9 📐 Science 📖 NCERT ✅ Free Access 🏆 CBSE · JEE
Share on
WhatsApp
Telegram
X / Twitter
Facebook
Instagram
Threads
Pinterest
LinkedIn
Quora
Discord
Reddit
Email
academia-aeternum.com/class-9/science/atoms-and-molecules/mcqs/ Copy link
💡
Exam tip: Sharing chapter notes with your study group creates a reinforcement loop. Teaching a concept is the fastest path to mastering it.

Frequently Asked Questions

Avogadro’s number is 6.022 × 10²³, the number of particles in one mole of substance.

An ion is an atom or molecule with a net electric charge due to electron gain or loss.

Atom is a single particle; molecule consists of two or more atoms bonded together.

The symbol for sodium is Na.

Polyatomic ions are ions formed by a group of atoms with an overall charge.

The chemical formula of water is H2O.

The subscript shows the number of atoms of that element in the molecule.

Diatomic molecules are molecules made up of two atoms, e.g., O2, N2, H2.

An empirical formula shows the simplest whole-number ratio of elements in a compound.

Monatomic: single atom (e.g., He); diatomic: two atoms (e.g., O2).

Recent Posts

    --:-- ⏱ Time
    ⚡ Progress 0 / 50 answered

    Atoms and Molecules — Learning Resources

    📄 Detailed Notes
    ✔️ True / False
    📌 Exercise
    💬 Q&A Discussion
    📝 Exercises
    ATOMS AND MOLECULES-Exercise
    📚
    ACADEMIA AETERNUM तमसो मा ज्योतिर्गमय · Est. 2025
    Sharing this chapter
    Atoms And Molecules | Science Class 9 | Academia Aeternum
    Atoms And Molecules | Science Class 9 | Academia Aeternum — Complete Notes & Solutions · academia-aeternum.com
    Understanding the concepts of atoms and molecules is a fundamental part of Class 9 Science. Chapter 3 of NCERT introduces learners to the building blocks of matter — how elements combine, the laws of chemical combination, and how to calculate molecular masses. To help students master these topics, this comprehensive set of 50 multiple choice questions (MCQs) with answers and detailed explanations covers every key concept from the chapter. These questions are ideal for CBSE Class 9 exams, school…
    🎓 Class 9 📐 Science 📖 NCERT ✅ Free Access 🏆 CBSE · JEE
    Share on
    WhatsApp
    Telegram
    X / Twitter
    Facebook
    Instagram
    Threads
    Pinterest
    LinkedIn
    Quora
    Discord
    Reddit
    Email
    academia-aeternum.com/class-9/science/atoms-and-molecules/mcqs/ Copy link
    💡
    Exam tip: Sharing chapter notes with your study group creates a reinforcement loop. Teaching a concept is the fastest path to mastering it.

    Get in Touch

    Let's Connect

    Questions, feedback, or suggestions?
    We'd love to hear from you.